The French horse feed evaluation systems and recommended ... · Tables of recommended allowances have been set up by INRA for mares, growing or working horses of light or heavy breeds

E L S E V I E R Livestock Production Science 40 (1994) 37-56

LIVESTOCK PRODUCTION

SCIENCE

The French horse feed evaluation systems and recommended allowances for energy and protein

W. Martin-Rosset*, M. Vermorel, M. Doreau, J.L. Tisserand, J. Andrieu INRA, Department of Herbivorous Husbandry and Nutrition, Research Centre of Clermont-Ferrand-Theix, 63122 Saint-Genes-Champanelle,

France

Accepted 27 April 1994

Abstract

New energy and protein systems were conceived and introduced in France by INRA for horse feed evaluation and recommended allowances. The net energy contents of feeds for maintenance are calculated from their metabolizable energy content, the estimated amounts of digestion end-products and their respective efficiencies for maintenance. The net energy value of feeds is related to that of barley and expressed in horse feed units (UFC). The validity of the system was tested extensively by INRA. The new protein system accounts for the amounts of absorbable amino acids. The horse digestible crude protein (MADC) content of feeds is calculated from the estimated amounts of amino acids absorbed from the small intestine and absorbed from the large intestine. In these two systems, the nutritive value of feeds can be predicted either from set of tables or from the chemical composition of feeds by using relationships established by INRA. The recommended allowances have been determined in UFC and MADC either by a factorial method or by feeding experiments according to the physiological function. With the feeding method, the allowances were determined by long term feeding experiments carded out by INRA with a high number of animals. Tables of recommended allowances have been set up by INRA for mares, growing or working horses of light or heavy breeds.

Keywords: Horse; Energy; Protein; Feeding; Requirement

1. Introduct ion

Thanks to an increase in knowledge since 1965 in the USA and in Europe, INRA elaborated new feeding systems for horses in France in 1984: the UFC system for energy and the M A D C 1 system for protein. These systems were performed to provide sets of tables that

* Corresponding author. * CHEVALRATION Software package - CEREOPA Ed. 16 rue

Claude Bernard, 75231 PARIS C6dex 05. 1 UFC: Unite Fouragire Cheval (Horse Feed Unit); MADC: Mati-

6res Azot6es Digestibles Cheval (Horse Digestible Crude Protein).

0301-6226/94/$07.00 © 1994 Elsevier Science B.V. All rights reserved SSDI0301-6226(94)00038-9

give respectively the nutritive value of the feeds and the nutrient requirements of the horses. Both are expressed according to the same feed evaluation systems either UFC for energy or MADC for protein.

These systems must allow:

1 an accurate comparison of the nutritive value of feeds

2 the formulation of well balanced rations to achieve a production goal

3 the prediction of performance of the animal when amount and quality of rations are known.

These systems and the proposed feeding standards were updated in 1990 by the same INRA group on the

38 W. Martin-Rosset et al. / Livestock Production Science 40 (1994) 37-56

basis of further experiments and many feeding trials (INRA, 1990).

GE GE = f(CP) £NP,.A 1978-1988

] Concent ra te* [ GE = f (CP ÷ E E + CF + NFE) Hoffmann et at.. 1971

1. Feed evaluat ion systems D E DE=GE xdE

[-~---'~---] dE = f (dMO) INRA-PRSP(1),

1.1. The Horse Feed Unit system (UFC)

A horse net energy system was conceived and introduced in France by Vermorel-Jarrige and Martin-Ros- set in 1984 due to the large difference in the efficiency of digestible energy (DE) or metabolisable energy (ME) utilisation of feeds (forages vs. concentrates) for maintenance, work and fattening as previously pointed out by Wolffet al., (1877-1895) and Grandeau et al. (1882-1904) with feeding trials, by Fingerling (1931-1939) and Hintz (1968) by indirect calorimetry.

The French Horse Net Energy (NE) system is based on: - the DE content of feeds as measured in horses - the ratio between ME and DE as measured in horses - the efficiency of ME utilization for maintenance

(km) calculated from: the assumed proportions of absorbed energy supplied by the various nutrients the efficiencies of ME utilisation for maintenance of the main nutrients.

Its validity was extensively tested in the years 1985- 1992 by indirect calorimetry balances (Vermorel and Martin-Rosset, 1991; Vermorel and Martin-Rosset, 1993 ) and feeding trials (Martin-Rosset and Vermorel, 1991 ). The scientific basis and structure of the system have been extensively described by Vermorel and Mar- tin-Rosset (1993). All the data are now available to calculate the NE value of feeds through a step-wise procedure (Fig. 1).

In this system the NE content of feeds is related to that of a reference feed (barley) and expressed in Horse Feed Unit (UFC). This unit corresponds to the NE value (2250 kcai) o f one kg of standard barley (87% DM) in horse at maintenance as the maintenance expenses account the largest part of total energy expenses, as much as 50-90% according to animals type.

The UFC value of a particular feed is calculated by dividing its NE content (in kcal) by that of barley (2250 kcal). The net energy value of feeds, expressed

M E M E / D E ~ - - ~ - - ~ M E / D E . f (CF, CP, CC)

INRA ME/DE = f (CF, CP) [

(CF, CP, CC, ± DOM)*

. ~ ~ ~cF, cP, cc, ± noM~* I a a ~ s L ~ , ~ - s } ~ (CF, CP)* [ CRRlgKL8 BY PRODUL'YI~ J ~

N E NE = M E x k m

Feed NE Value U F C . Feed INK content Bar l ey NE content

* The moat s ignif icant variables o f the equat ions o f predict ion

GE : Gross Energy DE : Digestible Energy CP : Crude Protein

ME : Metabolisable Energy CF : Crude Fiber

NE : Net Energy EE : Ether extract (1) PRSP : Rehash Station for DOM : Dig~tible Organic Matter /fiFE : Nitreg~ Free Ezt~t Cattle, Sheep and Ho~ Husb~dry dOM : Digestibility of Organic Matter CC : Cytopl~k Carbohydrates LELYSTAD. THE NETHERLANDS

Fig. 1. Prediction of the NE values of feeds in the UFC system.

in UFC per kg of dry matter (DM), in the INRA tables ( 1984 and 1990) is for example: corn 1.35; barley 1.16; oat 1.01; maize silage 0.88; hay 0.67-0.40; straw 0.28. The greatest differences between feeds pertain to the digestibility of organic matter or energy, but steps from DE to ME then to NE for maintenance increase the discrepancy of energy values between feeds when the cell wall content (CF) of the feed increases (Fig. 2). The energy value of straw equals 41% of that of barley in DE, 37% in ME and 29% in NE (UFC).

The expression of the NE values of feedstuffs related to that of barley as in the other well known feed unit systems has several limits and advantages.

Limits of accuracy of the UFC system focuse in the estimates of the percentage of absorbed energy supplied by the main nutrients as there is a lack of new data obtained in recent digestion trials with the exception of the studies of Kienzle et al. 1992. But large error in these estimates have relatively small effects on the value of km (Vermorel and Martin-Rosset, 1993). Using km to predict the energy value of feeds for horses in various physiological situations might cause errors in the cases of lactation and growth as well. But the km/kl ratio might be relatively constant whatever the feeds in horses as it has been pointed out in ruminants

W. Martin-Rosset et al. / Livestock Production Science 40 (1994) 37-56 39

o 1,0"

O,8

O,S

O,4

0,2-

0

UFC

Alta/fa Good Bad S t r a w Corn Bar ley Oats dohy hay hay

Fig. 2. Ranges in the energy values of feedstuffs in relation to barley, whether expressed as digestible energy (DE) or net energy ( UFC ). Value

per kg of dry matter content, feedstuffs classified according to their crude fiber (CF) content.

(Van Es, 1975). As a result the UFC value of feeds should be close for maintenance and lactation. The discrespancies in efficiency of ME utilization for maintenance and fattening or growth are probably higher

than for lactation namely for forages, but requirements for growth account for only 10-20% of total energy requirements in light breeds and 20-40% in heavy breeds (Agabriel et al. 1984).

%

60"

50"

40-

30.

20.

10.

0

D

0 mm o

oo A

Oss

0

D •

8 10 1 '~ 14 16

C r u d e prot~ims (% DM)

18 20

%

~0'

50'

40

30

20

10

0

0

O ° o

0 0

o

0 0

D

20 SO 40 50 60 70 80

Nit rogen i n ~ k e (g/day)

::: ........ ~ 100 % About 50 % Low 0 % ,r

G r o u n d hay • • A []

Fig. 3. Apparent digestibility in the small intestine (in %) of consumed nitrogen in equine related to (A) crude protein content of diets (horse - pony - donkey) and (B) amount of nitrogen ingested per day (pony). Data obtained with markers by Reintour et al., 1969; Hertel et al., 1970; Hintz et al., 1971; Woltev and Goui, 1976; Klendshot et al., 1974., Haley et al., 1979; Gibbs et al., 1979; Martin-Rosset et al., 1987.


Table 1 Apparent and true digestion of nitrogen in the digestive tract of fistulated pony (from Klendshoj et al., 1979; Haley et al., 1979; Gibbs et al., 1981)

Feeds

Nitrogen intake Apparent digestibility measured (in % of N intake)

True digestibility calculated (1) (in % of N intake)

CP% N intake Small Large Total Small Large Total g/day intestine intestine tract intestine intestine tract

Bermuda Grass Hay (50), 12.2 48.1 46.2 22.5 68.7 69 13 82 Crimped Oats (50)

Bermuda Grass Hay (50), 12.2 48.9 35.2 35.7 70.9 58 32 90 Micronized Oats (50)

Bermuda Grass Hay (50), 12.2 51.0 51.2 10.9 62.1 73 2 75 Crimped Milo (50)

Bermuda Grass Hay (50), 12.2 48.0 51.7 13.4 65.1 74 5 79 Micronized Milo (50)

Bermuda Grass Hay (50), 12.2 55.2 46.0 22.1 68.1 70 13 83 Oats (50)

Bermuda Grass Hay (50), 12.2 59.0 50.8 21.7 72.5 73 13 86 Soyabean meal (50)

Bermuda Grass Hay (50), 12.2 61.8 55.0 17.6 72.6 77 8 85 Cotton seed meal (50)

Bermuda Hay 11.7 23.6 1.3 47.5 57.1 36 37 73 Alfalfa Hay 15.0 29.8 1.3 64.8 66.1 22 57 79 Alfalfa Hay 18. I 35.7 21.0 52.8 73.8 38 46 84

1 True digestibility calculation: amount of endogenous nitrogen per kg of dry matter has been assessed to be 5 g in ileal flux (from data in ruminants and pigs and Gibbs et al., 1988); and 3 g in the faeces (from Meyer, 1983).

The UFC value of feeds is the same for maintenance and work as energy is mainly used for ATP production.

This aspect was pointed out by Armsby (1917) in his famous handbook on the nutrition of farm animals; the variation in NE content of feeds with physiological functions is buffered by the variations in NE of barley. Feeds are frequently compared rather in terms of substitution value than in NE absolute value from the feeding or business point of view. This substitution system is sound. The energy supplies of feeds are additive as well as energy requirements. The UFC values of exotic feeds can be more easily derived from those obtained in ruminants or pigs. Feed unit expression allow the best integration of previous data on energy value of feeds or energy requirement of horses from European studies (SFU, FFU. . . ).

A feed unit system is more pratical: the nutritive value of one kg of barley is better understood than one kg of TDN, a megacalorie or a megajoule. It has been taught, diffused and used for decades.

The NE system was officialy introduced in the Neth- erlands in 1992. It is more and more used in Italy and

in Spain since the INRA books ( 1984 and 1990) have been translated into Italian and Spanish (the English translation is being prepared and will be presented at the EAAP Norway meeting in 1996).

1.2. The Horse Digestible Crude Protein System

(MADC)

The protein value of feedstuffs is usually expressed as Digestible Crude Protein, (DCP) (NRC, 1978; Fut- termittel, tabellen, 1984). It corresponds to the crude protein (CP) content of feedstuffs multiplied by the apparent digestibility coefficient.

The apparent CP digestibility of many feedstuffs has been measured in horses (cf. reviews by Schneider, 1947; Meyer, 1983; Martin-Rosset et al., 1984). It partly evaluates the difference between forages and concentrates in the amount of amino acids ( A A ) supplied by feeds and absorbed, but it does not differentiate A A and ammonia proportions in the DCP.

W. Martin-Rosset et al. /Livestock Production Science 40 (1994) 37-56 41

The protein value of feedstuffs depends also on true

digestibili ty and respective proportions of CP digested in the small and large intestines.

On the basis of studies conducted with markers in

slaughtered or fistulated animals apparent digestibility in the small intestine (Fig. 3) or ileal digestibility increases with protein intake and, subsequently, with

the protein content of the diet. It varies from 10-20% with hay diets, to 35-55% with diets that have 50 -

100% concentrates. A considerable proportion of feed proteins and endogenous crude protein (digestive

secretions, urea) reaches the large intestine. We have

assumed that non protein nitrogen (NPN) of feeds is absorbed in the small intestine. If we assume that the

amount of endogenous nitrogen reaching the caecum

and collected in faeces are respectively 5 and 3 g / k g

DM intake (Table 1), the true digestibility of nitrogen from the small intestine can be estimated on the basis of measurements made with fistulated animals. True digestibility is much higher than apparent digestibility.

On average it is 20--40% for hays (with 12-18% of C P / D M ) , fed alone and 60-75% with mixed diets

(with a minimum of 12% C P / D M ) (Table 1). It may be admitted that the true protein digestibility

of concentrates is about 80% if retention time of feed in the stomach is long enough (Cordelet, 1990). It is

not far from the value determined for pigs (Darcy et

al., 1982). True digestibility should be lower for hay although it is overestimated for proteins, since NPN

digestion is very high. This was shown in the work of

Table 2 Assessment of the amount of absorbable intestinal amino acids (expressed in AIAA ) provided by some feedstuffs. Comparison between forages and concentrates (in g/kg DM) a

Feedstuffs Crude protein Small intestine Large intestine Total tract

Total non-aminated Entry True AIAA Entry True AIAA AIAA MADC DCP g g g digestibility g g(1) digestibility %~2) g g g

Rich concentrates 180 9 171 0.85 145 26 0.90 10 2 147 148 (crude fiber 8%) 30 7 152

0.75 128 43 10 4 132 30 12 140

Green grassatearly 180 18 162 0.70 113 49 0.80 10 4 117 128 grazing stage 30 12 125

0.60 97 65 10 5 102 30 16 113

Barley-commixture 110 5 105 0.85 89 16 0.90 10 1 90 90 30 4 93

0/75 79 26 10 2 81 30 7 86

Grass hay (m heading) 110 11 99 0.50 50 49 0.75 10 4 54 65 30 11 61

0.40 40 59 10 4 44 30 13 53

Grass silage 110 28 82 0.50 41 41 0.75 10 3 44 65 30 9 50

0.40 33 49 10 4 37 30 11 44

Jarrige and Tisserand, 1984. ( l )Entry: in gr of aminated nitrogen provided by feeds. (2) Percentage of alimentary proteins absorbed as amino acids and peptides.

AIAA: Absorbable Intestinal Amino Acid.


Glade (1983) where the apparent digestibility of sol- uble protein residue obtained with neutral detergent fibre (NDF) was much higher than that of insoluble protein.

Thus, true protein digestibility in the small intestine was estimated by Jarrige and Tisserand (1984) as: * 60-70% for grass * 60% for dehydrated alfalfa * 30-45% for hays according to vegetative stage at

harvest Feed proteins which escape enzymatic digestion in

the small intestine and endogenous proteins are degraded in the large intestine as amino acid (AA), peptides and ammonia and resynthesised to microbial protein, according to available energy (Reitnour, 1979; Glade, 1984) and the type of nitrogen consumed (Tis- serand and Masson, 1976; Glade, 1984). Microbial protein thereafter provides free AA and ammonia absorbed in the colon (Slade et al., 1971 ; Goodbee and Slade, 1972; Wysocki and Baker, 1975).

However, a proportion of feed protein (the non digestible CP) is excreted in the faeces: it is related to the CP content of forages (Martin-Rosset et al., 1984). Certainly the proportion of undigested feed protein excreted in the faeces is low but it cannot be distinguished from endogenous and microbial nitrogen excreted. This makes difficult the estimation of protein nitrogen proportion which can be absorbed as AA and which enhances that absorbed in the small intestine.

Nitrogen balance can be improved in ponies fed poor nitrogen diets supplemented with NPN (urea, etc) by enhancing the microbial population of the caecum. Measurements using labelled nitrogen infused in the caecum of ponies do show that microflora can synthe- size proteins which are thereafter degraded and absorbed as essential AA particularly (EAA) (cf. review of Meyer, 1983; Jarrige et Tisserand, 1984).

It was assumed that only 10-30% of nitrogen digested in the large intestine would be absorbed as AA or peptides on the basis of work conducted since 1970 on microbial protein synthesis, and on efficiency of the absorption of AA produced by microbial protein pro- teolysis (cf. review of Jarrige and Tisserand, t984 and recent investigation of Schubert, 1992). Those assumed values are very consistent with what is known in monogastric animals (Rerat, 1981) or in ruminants (INRA, 1978).

From the above considerations the protein value of feedstuffs for the horse is referred to as the sum of feed and microbial AA absorbed in the small and large intestines respectively and expressed in Horse digestible crude protein (MADC).

The attempt to evaluate amounts of absorbable AA in the whole digestive tract on the basis of true digestibility measured with markers in the small intestine and assumed in the large intestine, point out that DCP over- estimates the value of forage expressed in MADC by 10-30% (Table 2). As a result, MADC content of the main group of forages is calculated by reducing their DCP content by: - 10% for green forages, - 15% for hay and dehydrated forages - 30% for good quality grass silages or multiplying DCP content respectively by a factor K which is 0.90, 0.85, 0.70 for the forages listed previously.

This type of expression allows comparisons and substitution of feedstuffs in the diets as in the UFC system. In a few situations, the expression has to be defined by EAA content for specific requirements (i.e. lysine, for growth).

2. Prediction of energy and protein value of feeds

The nutritive value of feeds can be predicted in the French systems, either from the feed tables or calculated from the chemical composition of feeds by using the appropriate relationships.

2.1. Feed tables

Feed tables were set up for horses by INRA in 1984 and 1990. The chemical composition was drawn from tables for Ruminants in the case of forages (INRA, 1978 and 1981) and from tables for Monogastric (INRA, 1984) or(and) ruminants in the case of concentrates and byproducts.

The digestibility of organic matter (dOM%) of fresh forages and hays was drawn from the digestibility measurements carried out by INRA (Martin-Rosset et al., 1984). dOM% of 33 forages was determined in 5 or 6 light horses fed near maintenance with total col- lection of faeces during 6 days after a 14 day-adaptation period. Simultaneous measurements of dOM of these

W. Martin-Rosset et aL / Livestock Production Science 40 (1994) 37-56

Table 3 Relationship between DCP content ( g / k g DM) and CP content ( g / k g DM) in forages ~

43

n Relationships RSD R

Fresh forages Natural grassland, grasses, 14 ~ DCP = - 27.33 + 0.8614 CP 5:7.7 0.967 and legumes L DCP = - 74.52 + 0.9568 CP 5:6.3 0.980

+ 0 . 1 1 6 7 C F

Hays Natural grassland grasses 47 DCP = - 25.96 + 0.8357 CP + 7.1 0.968 Legumes 25 DCP = - 29.95 + 0.8673 + 9.2 0.933

All Forages 72 DCP = - 27.57 + 0.8441 + 8.6 0.964

' Martin-Rosset et al., 1984.

33 forages in Horse (dOMn) and Wethers (dOMw) allowed to complete the following relationships for fresh forages or hays (Martin-Rosset et al., 1984).

natural grasslands and grasses:

dOMH = - 14.91 + 1.1544 dOMw

RSD_2.3 R=0.980 N = 1 8 (1)

legumes:

dOMH = - 9.94 + 1.1262 dOMw

RSD_2 .6 R=0.844 N = 15 (2)

These relationships were used to predict dOMH of 114 forages from dOM obtained with wethers (INRA, 1978). Those relationships were used also to estimate dOM of grass silages as there were no similar relationship for silages. As a result the dOM of grass silages is given in the tables as an indication. But recent data obtained by Smolders et al. (1990) support the values. For other forages such as maize silage, dehydrated pel- leted lucerne, which is the commercial form, alkali treated straw or poor quality hay were drawn directly

from digestibility experiments carried out by INRA (Martin-Rosset et al., 1984).

The dOM of forages given in the tables can be used either in horses fed restricted or ad lib. as there is no effect of the feeding level on dOM (cf. review of Mar- tin-Rosset et al., 1984 and Martin-Rosset et al., 1990).

Most of the hays listed in the tables are expected to be offered in loose form for effect of grinding and/or pelleting on digestibility of forages are contradictory due to a reversing effect with the feeding level (Haen- lein et al., 1966; Wolter et al., 1975).

The DCP content of all forages were estimated using relationships between DCP and CP content of forages studied by INRA and drawn from the literature (Table 3). The DCP content were corrected by the appropriate factor K to be expressed in MADC.

However, the nutritive value of forages can be predicted directly with the tables when the botanical characteristics and the conditions at crop are known. Martin-Rosset et al. (1984); Chenost and Martin-Ros- set, (1985) pointed out that digestibilities of fresh forages were fairly well related to their characteristics at crop (mainly: species, cycle, and age) and to their

Table 4 Relationship between digestibi l i ty of organic matter (dOM%) and crude fiber (CF) content ( g / k g DM) in hays I

Botanical n Range of CF Relationships RSD R

content

Natural grassland 28 230-375 dOM = 87.89 - 0.1180 CF + 4.1 Grasses 19 295-390 dOM = 81.51 - 0.0792 CF + 6.3 Legumes 25 285-395 dOM = 90.52 - 0 . 0 9 9 5 CF + 3.7 All forages 72 230-395 dOM = 78.33 - 0.0746 CF 5:6.0

0.710 0.422

0.666 0.414

' Martin-Rosset et al., 1984.

44 w. Martin-Rosset et al. / Livestock Production Science 40 (1994) 37-56

conditions at crop for preserved forages. Recent data obtained by Smolders et al. (1990) supports the idea.

The OM and CP digestibilities of concentrates (cereals, cereals byproducts) come partly from digestibility experiments carried out by INRA and others (cf. review of Martin-Rosset et al., 1984) in horses fed forages supplemented with more than 25% of concentrates as the limits of the method for calculating their digestibility by difference is well known, when the percentage of concentrate in the diet decrease (Martin- Rosset and Dulphy, 1987). The digestibility was also drawn from pig tables when the CF content was less than 15% (peas, cakes, maize, starch) or were extrap- olated from pigs and ruminants tables in other cases (for examples: maize s tover- dehydrated potatoes pulp

- linseed meal - palm kernel meal - maize bran - molasses).

2.2. Calculation from chemical composition

Energy The NE value is calculated from gross energy (GE)

content of the feeds, the digestibility of energy (dE), the ratio between metabolisable energy (ME)and digestible energy (DE): ME/DE and from the efficiency of ME utilization for maintenance (km) (Ver- morel et al., 1984).

NE = GE x dE X (ME/DE) × km

dE, ME/DE and km are expressed as a fraction in the relationship

Gross energy In the absence of direct measurement the GE content

of green forages and hays (Y in kcal/kg OM) can be predicted from the CP content ( X g/kg OM) using the following equation (INRA, 1988).

Y = 4531 + A + 1.735 X Syx = 38 r = 0945

A = + 82: fresh lucerne or lowland permanent pasture (altitude < 700 m), hays from lowland and upland pastures.

A = - 11: Fresh red clover, sainfoin, upland permanent pasture, whole plant immature cereals (maize, wheat, barley etc.); hays from leys (lucerne, rye- grass).

A = - 71: fresh grasses (cocksfoot, rye-grass, etc.)

The GE content of silages can be predicted with specific relatonships: • direct cut grass silages (from INRA, 1988)

GE (kcal/kgOM) = 3910 + 2.450x + 169.6 pH x = CP content (g/kgOM)

• wilted grass silages (from Andrieu and Demar- quilly, 1987) GE (kcal/kgOM) = GE of green forages x 1.03

• maize silages (from INRA, 1988) -for silages with a dry matter content of less than

30% GE (kca l /kgOM)=4772

-for silages with a dry matter content higher than 30% GE (kcal/kgOM) =4678 -t- 110

The GE content of concentrates (kcal/kg OM or DM) can be calculated from their chemical composition expressed in g/kg OM or DM using the equation of Hoffmann et al. ( 1971 ).

GE=5.72 CP+9.50 EE+4.79 CF+4.17 N F E + A

were CP, EE, CF, NFE are respectively the content in crude protein, ether extract, crude fiber, nitrogen free extract. The A values proposed by Hoffmann et al. ( 1971 ) depends on the kind of feed cereals/grains byproducts/seeds, cakes/animal meal/roots and tubers.

Digestibility o f energy (dE) and digestible energy (DE) The DE of forages can be calculated from GE and

dE when dOM is known, dOM can be predicted from CF content for forages (Table 4). Furthermore dOM can be predicted directly by new routine methods: cel- lulase method or NIR (Andrieu and Martin-Rosset, 1993). There is no relationship to predict dOM of concentrates from their chemical composition, dOM of concentrates must be drawn from the tables.

The dE (%) of all feeds is related to dOM (%) by the new following relationship set up by INRA (France) and PRSP (Research Station for Cattle, Sheep and Horse Husbandry in the Netherlands) in 1992. It substitutes for the previous relationships established for forages and concentrates (INRA, 1984).

dE = 0.0340 + A + 0.9477 dOM

RSD=I .1 r 2=0.994 n=75

A = + 1.1 for concentrates

A = - 1.1 for forages

e.g., dE= 55.8% when dOM = 60% for forages

W. Martin-Rosset et al. / Livestock Production Science 40 (1994) 37-56

Table 5 Relationships between overall efficiency of ME for maintenance (km) and the chemical composition of feeds

45

R S D R 2

Forages (n = 47) 100 km = 71.64 - 0.0289 CF + 0.0148 CP 100 km=65.21-0.0178 CF+0.0181 CP + 0.0452 CC 100 km = 57.56 - 0.0110 CF + 0.0105 CP + 0.0270 CC + 0.0150 DOM

Cereals - legumes seeds (n = 22) 100 km = 82.27 - 0.0248 C F - 0.0160 CP 100 km = 72.34 + 0.0119 C F - 0.0081 CP + 0.0112 CC 1 0 0 km = 9 3 . 1 8 - 0.0490 CF - 0.0101 CP - 0.0127 DOM 100 km = 77.45 - 0.0060 CF + 0.0106 CC - 0.0054 DOM

Cereals -by products (n= 18) 100 km= 100.32 -0.0194 O M - 0.0120 CP-0.0530 CF 100 km=94.41-0.0237 O M - 0.0022 CP+0.0121 CC

Cakes (n=8) 100 km = 67.03 + 0.004261 CP + 0.01566 CC 100 km = 67.13 + 0.00278 CF + 0.00528 CP

+0.94 0.878 5:0.53 0.963 _ 0.40 0.980

+ 0.66 0.962 + 0.35 0.990 :1:0.59 0.971 5:0.32 0.992

+0.76 0.887 + 0.45 0.961

+ 0.29 0.900 + 0.44 0.700

OM: Organic matter; CF: Crude fiber; CP: Crude protein; CC: Cytoplasmic carbohydrates; DOM: Digestible Organic Matter. (g/kg DM).

As a result D E ( M c a l / k g D M ) can be calculated as

fol lows: D E = ( G E × dE) / (100)

By example D E = 2.47 M c a l / k g D M when GE = 4.43

M c a l / k g D M and dE = 55.8%

Metabolisable energy The content in M E is calculated f rom D E through

the M E / D E ratio according to the fo l lowing predict ion

equat ions where CF, CP, C C (cy top lasmic carbohy-

drates) are expressed in g / k g DM.

For all feeds: (forages and concentra tes)

1 0 0 ( M E / D E ) = 84.07 + 0 . 1 6 5 CF

wheat straw, to 0 .84-0 .88 for hays and 0.90--0.95 for

cereals.

Net Energy The N E of feeds is calculated f rom M E and the

overal l eff iciency of M E uti l ization ( k m ) . For each

kind o f feed km is predicted f rom the chemica l com-

posit ion (Table 5) .

The N E of each feed calculated in that way is related

to that o f barley and expressed Horse Feed Uni t ( U F C ) .

N E ( U F C ) = ( M E × k m / 2 2 5 0 )

- 0 . 2 7 6 C P + 0 . 1 8 4 C C

R S D +_ 1.37 R 2 = 0 . 4 5 n = 7 9

For protein rich feeds ( > 30% C P / D M )

1 0 0 ( M E / D E ) = 94.36 + 0.110 CF - 0.275 CP

R S D + l . 7 5 R Z = 0 . 1 7 n = 9 0

For beet pulp: 1 0 0 ( M E / D E ) = 89 obtained by Vermore l , Vernet

and Mart in-Rosset , 1988 (as equat ion for all feeds

underes t imated this va lue ) .

The M E / D E value calculated f rom these relationships ranged f rom 0 .78-0 .80 for oil meals , to 0.91 for

Application to standard barley: The Horse Feed Unit The energy value o f one kg standard barley ( 8 7 %

D M ) is as fol lows:

GE = 3854 k c a l / k g

d O M = 0.83

dE = 0.80 D E = 3076kca l /kg

M E / D E = 0.93 M E = 2864 k c a l / k g

km = 0.785 N E = 2250 k c a l / k g

1 U F C = 2250 kcal N E

One Horse Feed Uni t ( U F C ) is the energy content o f one kg of standard barley for maintenance.


Table 6

Prediction of the Horse Feed Unit (UFC) value ( /kg DM) of forages or concentrates from chemical composition

Forages (n = 4 7 )

UFC = 0.825 - 0.0011CF + 0.0006 CP

UFC= 0.568 - 0.0007 CF + 0.0007 CP + 0.0018 CC

UFC = - 0.124 + 0.0003 CC + 0.0013 DOM

UFC = - 0.0557 + 0.0006 CC + 0.2589 DE

Concentrates ( n = 51 )

UFC= 0.815 - 0.0009 CF + 0.0003 CP + 0.0006 CC

UFC= 0.131 - 0.0006 C F - 0.0003 CP + 0.00134 DOM UFC = - 0.730 - 0.0007 CP + 0.00057 OM + 0.3944 DE

UFC = - 0.134 + 0.0003 C F - 0.0004 CP + 0.0003 CC + 0.3160 DE

RSD( + ) R

0.043 0.832

0.031 0.922

0.012 0.988

0.007 0.996

0.060 0.931 0.041 0.967

0.033 0.979

0.017 0.995

OM: Organic matter; CF: Crude Fiber; CP: Crude Protein; CC: Cytoplasmic Carbohydrates; DOM: Digestible Organic Matter (g /kg DM). DE: Digestible Energy (Mcal/kg DM).

Forages and concentrates (raw materials) The UFC value of forages or concentrates can be

predicted directly from chemical composition with relationships recently produced by INRA and the contribution of PRSP in 1992 (Table 6). The accuracy of prediction (RSD) reach -I-0.007 and -I-0.017 UFC/ kg DM for the forages and the concentrates respectively when DE is introduced as covariable of chemical composition in the equation. The accuracy (RSD) is only + 0.043 and + 0.060 UFC/kg DM by using only CF, CP and CC as covariables in the equations.

Compound feeds The UFC value of compound feeds can be predicted

from chemical composition measured by routine anal- ysis which is quite useful for commercial purpose (Table 7).

The best accuracy is reached with starch and Van Soest components introduced as covariables of CP content. The differences between the UFC value predicted by the equations listed in the Table 7 and that calculated

with the additive method by using the UFC value of the ingredients incorporated in the compound feeds range from 0.2-1.3 UFC/100 kg OM depending on the criteria used.

The UFC value of compound feeds must be increased by 0.02 UFC for 1 percent of ether extract (EE) above 3.5% of EE in the compounds feeds as the relationships were performed for commercial feeds which contain no more than 3.0% of EE.

Protein The protein value of feeds in the horse is expressed

in MADC that is the DCP corrected for the proportion of CP which does not supply AA. MADC content (g / kg DM) is calculated from DCP (g /kg DM) content multiplied by a correction factor K which depends on the group of forages.

MADC = DCP × K

K = 0.90 for green forages K = 0.85 for hays and dehydrated forages

Table 7 Relationship to predict the Horse Feed Unit (UFC) value ( / 100 kg OM) of compound feeds from chemical composition

Relationships I RSD( + ) R

132.6 - 0.1037 C F O - 0.0135 CPO

133.3 - 0.1684 ADFO - 0.0096 CPI3 117.3-0.1605 CFO + 0.0051 CPO+0.0215 STAID 118.l -0 .1397 ADFO + 0.0082 CI:~ + 0.0214 STAO 121.9 - 0.0852 A D F O - 0.0287 NDFO - 0.0857 LIO + 0.0034 CPO

6.0 0.978

6.0 0.979 4.3 0.988 4.0 0.989 3. I 0.994

' UFC for 100 kg OM. CF: Crude Fiber; CP: Crude Protein; STA: Starch + sugars; ADF: Acid detergent fiber; NDF: Neutral detergent fiber; Li: Lignin. CF, CP,

ADF, NDF, Li, STA: g /kg organic matter ( 0 ) .


K = 0.80 for straws and their by-products with high lignin content K = 0.70 for good grass silages

The DCP content of forages can be predicted with the relationship given in Table 3. The DCP content (g/ kg DM)of cereals and their by-products can be predicted with the following relationship where CP is expressed in g/kg DM.

DCP = - 4.94 + 0.8533 CP

RSD___7.7 R=0.931 n=23

For the other concentrates the DCP content must be drawn from the tables.

pathological disorders related to large variation in work load and subsequent daily nutrient intake. The allowances can be estimated either by a factorial

method from metabolic data and/or by feeding experiments according to the physiological function. With the factorial method the amounts of energy or proteins retained or exported are divided by the metabolic efficiencies of metabolisable energy or the efficiencies of the digestible crude protein which are specific to the physiological function where these efficiencies are known. With the feeding method the allowances are determined by long term feeding trials (and energy or nitrogen balances) carried out with a high number of animals. In these experiments energy and nitrogen intakes are related to the true performances.

3. Requirements and recommended allowances

3.1. Definitions and methods of determination

In France nutrient requirements and allowances are clearly distinguished. The requirements stand for physiological expenditure of horses for maintenance, pregnancy, lactation, growth or exercise. The requirements are met by the nutrients supplied by the ration and by the body reserves when the amount of nutrients supplied is inadequate. The nutrient allowances represent the amount of the nutrients provided by an appropriate ration.

A recommended allowance is the amount of nutrients which should be supplied to horses to achieve a desirable level of performance allowed by their potential. The animals are assumed to be in good health, well managed and housed during the winter period. This should be considered as optimum allowances which cover either the requirements or slightly more or less than the requirements. For example exceptions are: • heavy mares where a moderate and controlled use

of body reserves is assumed during the winter period to reduce feed costs

• growing horses bred for school-tiding and hacking, where a limited growth is assumed during the winter period but a compensatory growth is expected during the subsequent summer period to achieve an optimum live weight at late braking in

• exercising horses where a moderate and controlled use of body reserves is assumed at short term (a few days) during the training period to avoid physio-

3.2. Energy requirements and recommended allowances

In horses as in other farm animals, maintenance and production requirement were artificially separated to facilitate calculation of total energy requirements, although overall metabolism is influenced by animal production levels.

Maintenance requirements have been assessed from feeding trials conducted at the end of the last century by Wolff et al. ( 1880-1898); Grandeau et al. ( 1888- 1904), former feeding standards (cf. review of Olsson and Ruudvere, 1955) and more recently from feeding trials (Breuer, 1968; Stillions and Nelson, 1972; Anderson et al., 1983) and indirect calorimentry trials (Hoffmann et al., 1967; Wooden et al., 1970; Knox et al., 1970) to 140 kcal DE/kg W0.75 or 120 kcal ME/ kg W0.75, thus to 84 kcal NE/kg W0.75 or 0.038 UFC / kg W0.75 (Vermorel et al., 1984). These requirements were recently checked with feeding and calorimetry trials in horses of light breeds (Martin-Rosset and Ver- morel, 1991). The daily requirements amount to 4.0 UFC for a gelding weighing 500 kg. The requirement depends on the breed, but increased by 10-20% for stallions (Axelsson, 1949; Nadal'Jak, 1961; Kossila et al., 1972), and by 5-15% for working horses to take into account, in exercising horses, the rise of the overall energy metabolism (Kellner, 1909) and the importance of the spontaneous activities related to the temper.

Increased expenses due to physical activity are calculated by the increase in oxygen consumption. For locomotion (walk- t ro t - galop) the increase in oxygen

48 W. Martin-Rosset et al. /Livestock Production Science 40 (1994) 37-56

Table 8 Variations of the energy expenditure with the velocity in the horse ~

Situation Velocity Energy expenditure (m/min)

(Kcal/min) Multiples of maintenance (maintenance = 1 )

Waiting without rider 0 I 1.5 I. 1 Waiting with rider 0 12 1.2 Walk 110 50 2.5 Slow trot 200 110 10 Normal trot 300 160 15 Fast trot* 500 350 35 Normal galop 350 210 20 Fast galop* 600 420 40 Maximum velocity* 600 60

' From INRA, 1984. The energy expenditures were calculated from the oxygen consumption (and oxygen debt) measured by Meixner, Hornicke and Ehrlein ( 1981 ) in horses of 560 kg body weight car- rying a load of 100 kg (rider + hack + apparatus). For walk, energy expenditure was calculated from data of Brody (1945), Hoffmann et al. (1967), Nadal'Jak ( 1961 ) and Zuntz and Hagemann (1898). * Value calculated from the maximum oxygen consumption of

horses estimated by Vermorel, Jarrige and Martin-Rosset (1984) and the oxygen debt.

L W O R K I N D O O R j

In~mlly V~y Ilghl LIghl I~loderale Intern

~ l ~ f ~ l begia.ing nd,r ~ilt~l n~er com~liU~n

E~rgycos1of 0.2-0.5 1,0-1,5 1,5 2,0 2,5 3,0 ~k UFC/h

W O R K O U T D O O R I

v~y light t.lghl :aoa.r.,. E . I ~

0,5 15 2,0 2,5 2,5 3,5

]f E D D

Gai t Walk Normal trot Normal galop l u m p i n g

Veloci ty 100 - 140 200 - 240 300 500

Fig. 4. Estimation of energy cost of one hour of exercise to add to daily maintenance requirement in saddle horses according to the type and duration of the work (INRA, 1984).

consumption is linearly related to velocity (Karlsen and Nadal'Jak, 1964; Meixner et al., 1981; Thomas and Fregin, 1981; H6rnicke et al., 1983). From all these data, we have calculated the energy costs of locomotion per meter/min including the oxygen debt, at standard velocities for different gaits in a 560 kg horse and riding

with a 100 kg load: rider+saddlery (Table 8). We have evaluated energy allowances for a standardised hour of work of a horse used in the most common practical situations, by dividing the hour into the different periods of work intensity multiplied by the fore- going estimated unitary energy cost (Fig. 4). The hourly costs are much higher than those suggested by the NRC (1978), but they cannot easily be compared to the new requirements ofNRC (1989) as the duration and intensity of daily work is not precisely defined. The reliability of our estimates was tested in long term feeding trials conducted with groups of 20-80 saddle horses at the National Riding School of Saumur or in other riding-schools.

For draught the total energy expense is the sum of energy expenses for locomotion and load pulling. We have preferred to borrow energy requirements for work from former standards (Jespersen, 1949) recalculated in terms of Scandinavian Feed Unit (ScFU) by Olsson and Ruudvere, 1955 because they were set up from feeding trials and practical observations, which were more reliable than assessments based on oxygen consumption as measured by Brody (1945) and Nadal'Jak ( 1961 ) on a very small numbers of horses.

Pregnancy and lactation requirements above maintenance have been estimated by a factorial method (Martin-Rosset and Doreau, 1984). The increase in energy content of the foetus was calculated by multiplying the foetus weight gain calculated from the data of Dusek, (1966); Den Engelsen (1966); Meyer and

Table 9 Weight gain and composition of the foetus a

Months Weight gain in % of Gross energy Protein content birth weight content kcal/kg (%) (1) (2) (2)

8th \ 19 1000 11,5 9th J 11 oo 13,0

lOth 30 1180 15,3 l lth 31 1280 17,1

a from Doreau, unpublished. ~ Drawn from Dusek (1966) and Den Engelsen (1966). 2 Drawn from Meyer and Ahlswede (1976).

Energy fixed in the conceptus: LBW of foal × gross energy content of foetus x 1.20 (for taking account of energy fixed in foetal annexes, uterus and udder) from Martin-Rosset and Doreau (1984). 14, 41 and 45% of energy is deposited in the 8-9 months, 10th month and 1 lth month respectively. Efficiency of metabolisable energy for pregnancy was expected to be 25%.


Table 10 Milk yield and composition

Months Milk yield Milk composition (kg/100 kg LW) l

Energy Protein (Kcal/kg) 2 (g/kg) 2

1 st 3.0 575 24 2nd 2.5 500 24 3rd 2.5 500 24 4th 2.0 475 21

Doreau and Boulot (1989). 2 Doreau et al. (1988).

In the first edition of the INRA recommandation (1984) the requirements were calculated with the available data (Martin- Rosset and Doreau, 1984), but the knowledge has increased a great deal since then.

Alhswede (1976) to estimate the amount of energy retained by the foetus (Table 9). The efficiency of energy utilization for pregnancy was estimated to be 25% (mean between those in cows and in sows in the absence of measurements in mares). The amount of energy fixed in the conceptus (foetus + adnexa + placenta) and udder, calculated by multiplying energy content of foetus by 1.20 to take account of energy fixed in the foetal adnexa, uterus and udder (Martin- Roset et Doreau, 1984), increase daily from 152 kcal to 467 kcal/100 kg LW/day between the 8th and the l lth month of pregnancy (Doreau unpublished). In lactation, the amounts of energy exported as milk was calculated thanks to better estimates of milk production and energy content (Table 10). Efficiency of energy utilization for milk production was estimated to be 65 % from those obtained in the cow and the sow. The energy requirement for milk production is 0.31 -0 .27 and 0.26 UFC/kg for the 1 st month, the 2nd and 3rd months and over the 4th month of lactation respectively. As a result the daily requirement for pregnancy, in late pregnancy (8th to 1 lth months) and for milk production, in early lactation (0-3th months) is 0.1-0.3 time and 0.9-0.6 time the maintenance requirements respectively. However, the recommended energy allowances were estimated on the basis of many feeding trials conducted with mares of light or heavy breeds fed different diets to take in account the possibility of body reserve utilization. Two levels of energy allowances: high level (HL) or low level (LL) were suggested according to

the breed (heavy vs. light) and body condition score (cf. Table 11).

In heavy mares energy allowances account for: • 100% (HL) or 80% (LL) of total energy require-

ment of dry, pregnant and late lactating mares (period 1).

• 110% (HL) or 90% (LL) of total energy requirement in early lactation (period 2). These levels of energy allowances were suggested

for two reasons: • a moderate undernutrition in late pregnancy has no

significant effect on the body weight and health of the foal at birth and its growth if the body condition score of the mare is good in early lactation,

• the effects of undernutrition in early lactation on the reproductive capacity of the mare are not well known. In light mares energy allowances account for:

• 110% (HL) or90% (LL) inperiod 1 • 120% (HL) or 110% (LL) in period 2

The suggested levels are higher for mares of light breeds to take into account the requirements of foals devoted to competition.

Growth energy requirements have been evaluated from feeding trials (Agabriel et al., 1984; Bigot et al., 1987), in which UFC intake, weight, weight gain of young horses were precisely measured, for three reasons: • the energy requirement for maintenance (kg

L W °75) varies with breed and the growth rate. The variation in maintenance requirements due to breed is known only in the adult. Maintenance requirement accounts for 60-90% of total energy requirement of the growing horse.

• the amount of fixed energy per kg weight gain computed from the chemical composition of different tissues was determined only in heavy breeds (Mar- tin-Rosset et al., 1983)

• the efficiency of metabolisable energy utilization for growth is not known yet. Energy allowances were computed according to

weight (W) and weight gain (G) of young horses using a relationship established from the results of feeding trials, and according to the following model drawn from the growing bull (Geay et al., 1978; Robelin, 1979) :

UFC/kg W°'7S/day = a + bG 14


Table 11

Feeding standards for mares: Recommanded nutrient allowances - Mare of light breed - 500 kg mature live weight* (INRA, 1990)

Physiological state Daily allowances

UFC

Low High level (e) level ( ~

MADC Ca P Mg Na Daily feed (3

(g) (g) (g) (g) (g) (kg DM)**

Dry mare or early pregnant mare 3.8 4.6 295 25 15 7 12 6.0-8.5

Pregnant mare 8th and 9th months 4.1 5.0 340 29 18 7 12 6.5-9.0 10th month 4.7 5.7 460 38 26 7 12 7.0-10.5 1 lth month 4.8 5.8 485 39 28 7 12 7.5-11.0

Lactating mare 1st month 8.9 10.7 950 61 55 10 15 12.0-15.0 2nd and 3rd month 7.6 9.2 770 47 40 9 14 10.0-15.0 4th month to weaning 6.1 7.5 660 39 32 8 13 8.0-12.5

* Live weight 24 hours after foaling; **DM: Dry matter. (~>For mares whose offsprings are used in competition with the exception of the mares that are fat (body condition score > 4; cflNRA, 1990).

Other mares (body condition score < 2.5) and mares wintered outdoor or matted at 3 years old. (2)Other cases. (3)The lower values are used with high proportion of concentrate in the diet and the higher with hay based diet values.

a: coefficient of maintenance requirement G: average daily gain: kg/d

The validity of the exponent 1.4 was checked from the results of slaughter experiments in young heavy horses (Agabriel et al., 1984).

The relationships for the growing horse of light breeds are given in the Table 12. For 1 kg of daily gain total requirement accounts for 4.9 UFC at 250 kg BW and 6.4 UFC at 350 kg BW. The increase deals with the maintenance requirements: + 1.1 UFC (3.8 UFC at 250 kg BW compared to 4.9 UFC at 350 kg BW) and with the cost of 1 kg of body gain: + 0.4 UFC ( 1.1 UFC at 250 kg BW compared to 1.5 UFC at 350 kg BW). At the same body weight: 300 kg, maintenance requirements reach 4.3 UFC but the cost of 1 kg of body gain increase with the level of growth + 0.8 UFC when growth requirement calculated for 500 g daily gain (0,5 UFC) are compared with the requirement for 1000 g daily gain ( 1.3 UFC).

Two levels of allowances were suggested according to the goal of production (horses produeed for school riding and hacking vs. horses produced for competition) and the growth potential of the young horses (Table 13):

optimal level for high growth (close to genetic potential) in young horses bred for competition, moderate level for limited growth in young horses bred for hacking but having compensatory growth on pasture.

3.3. Protein requirements and recommended allowances

On the basis of the nitrogen balance set up by Slade et al. (1970), Prior et al. (1974), we have estimated maintenance requirements to be 2.4 g DCP/kg W °75. (DCP: Digestible Crude Protein). Expressed in MADC, allowances are 10"15% higher: 2.8 g MADC/ kg W0.75, since the DCP content of forages has been reduced by 10-20%, to be expressed in MADC. Daily allowances reach 295 g MADC for horses weighing 500 kg. Hence, recommendations are very close to those suggested by the NRC, 1978:2.8 DCP/kg W0.75. INRA recommendations cannot be compared to the new requirements suggested in crude protein (CP), by NRC, 1989. The former requirements were compiled by Olsson and Ruudvere (1955). However, they are lower than those calculated with the factorial


Table 12 Requirement for growth

Energy: relationship between daily energy intake and live weight Protein: relationship between daily protein intake and live and growth in young horses of light breeds t weight and growth in young horses of light breeds UFC/day/kgW "7~ = a + bG TM g MADC/day = aW '75 + bG

Ages (months) a b Ages (months) a b

6--2 0.0602 0.0183 6-12 3,5 450 18-24 0.0594 0.0252 18-24 2,8 270 30-36 0.0594 0.0252 30-36 2,8 270

ta: Coefficient of maintenance. G: average daily gain (kg/day).

Data from Agabriel et al., Unpublished results.

method (Meyer , 1983) as this author took into account the possibilities of storing proteins.

All the feeding trials, digestion studies and nitrogen balances carried out, show that the A A composit ion of the common diets for adult horses at maintenance is of no importance and that NPN (urea particularly) can be successfully used by the horse if the fermentable energy supply in the large intestine is sufficient.

Work protein expenses are unknown. They could increase more slowly than energy expenses in relation to intensity and duration of work, if energy supply is sufficient to prevent body protein mobilisation (Kell- ner, 1909). Thus, there is some reason to relate protein and energy supply for work as for protein synthesis where the protein gain is posit ively related to the protein and energy contents of the diet. A supply of 60 - 65 M A D C / U F C beyond maintenance requirements seems satisfactory for the adult horse at work as for-

mely pointed out by different workers (cf. review of Olsson and Ruudvere, 1955). This ratio is generally kept constant in well trained adult horses when the work load increases. A greater supply should be necessary for the yearling during training to enable good increases in muscular mass, in the concentrations of myoglobin and in enzymes responsible for muscular metabolism and to prevent anemia. For the human athlete protein supply should be increased by 20% at the beginning of training and by 100% during intensive training (Wil l - more and Freund, 1984).

The protein requirements for pregnancy beyond maintenance were calculated by the factorial method (Martin-Rosset and Doreau, 1984). The total amount of daily protein retention was calculated by dividing the amount of protein fixed in the conceptus (Table 9) by the metabolic efficiency of DCP for that function. It has been stated at 55%, whereas Meyer (1983) and

Table 13 Feeding standards for the growing horses I. Recommended nutrient allowances - Horses of light breed - 500 kg mature body weight

Age Mean body Growth (months) weight during

the period Level Dally gain (kg) (g/d)

Dally allowances

UFC MADC Ca P Mg Na (g) (g) (g) (g) (g)

Daily Feed* (kg/DM)**

320 optimal 700-800 5,5 8-12

280 moderate 400-500 4,5 470 optimal 400-500 6,8 20-24 440 moderate 150-200 6,0 490 optimal 150-250 6,5

32-36 470 moderate 0-100 6,0

590 39 22 10 12 5.5-8.0 440 28 16 9 9 5.0-7.5 420 36 20 10 13 7.5-10.0 330 28 16 9 12 7.0-10.0 330 30 18 10 12 8.0-11.0 260 25 15 8 12 7.5-10.0

* The lower values are used with high proportion of concentrates in the diet and the higher values **DM: Dry matter. 1 From INRA, 1990.

with hay based diet.

52 W. Martin-Rosset et al. /Livestock Production Science 40 (1994) 37-56

NRC (1978) assumed that it was 50 and 45% respectively. That efficiency is slightly lower than the value used for pigs and ruminants: 60%. The daily amount of proteins fixed in the conceptus (foetus + adenexa+placenta+ udder) reach 5.0 g/100 kgLW and 21 g/100 kg LW between the 8 and the 1 lth months pregnancy. The recommended allowances given in the INRA table ( 1984 and 1990) account for 100% of the requirements (Table 11 ).

The protein requirements for milk production (above maintenance requirements) were also calculated by the factorial method on the bases of the amount of proteins secreted daily in the milk (Table 10) and of the metabolic efficiency of DCP estimated to be 55%. This efficiency is close to those suggested by Meyer ( 1983): 50-60% and those suggested by Bros- ter (1972) for true DCP: 50-55%. The efficiency retained by NRC, 1978 and 1989: 69% for the DCP, seems too high if we refer to the efficiency measured in ruminants (60% for the DCP). The protein allowances suggested (Table 11) stand for 100% of the requirements as the influence of the protein deficiency in the mare is not well known (Martin-Rosset and Doreau, 1984; Doreau et al., 1988). The protein allowances per kg of milk stand for 44 g, 38 g and 36 g for the 1 st month, 2nd and 3rd month and for the 4th month of lactation, respectively.

Protein requirements of growing horses (above maintenance) were calculated from protein retention. The latter can be determined accurately from the composition of empty body weight and weight gain. This was defined on the basis of anatomical composition data on horses of heavy breeds slaughtered at different ages (Martin-Rosset et al., 1983 ), after several feeding trials (Agabriel et al., 1984). Protein requirements of heavy breeds were estimated by the factorial method because all the feeding trials conducted were designed to define the optimum CP content of the diet or the effect of feed protein quality on the growth of the young horse. The efficiency of MADC stated was 45% as suggested by the NRC (1978). We suggested supply- ing 3.5 g MADC/kg W °75 for maintenance in the young horse until one year of age, instead of 2.8 g MADC/kg W °75 to take into account of the faster turnover of body protein: 25 % as measured in other species (Reeds and Harris, 1982). In light breeds protein requirements were calculated by using a mathematical model similar to that used for energy (Table 12) as there were

enough INRA trials designed to study effect of the CP content of the diet on average daily gain.

Two levels of allowance were suggested in growing horses as for energy considering the goal of production, genetic potential of the animal and the use of compensatory growth on pasture (Table 13).

We have kept to the allowances suggested by NRC for lysine (the single AA recognized as limiting): 0.6% of DM in the diet for the 6 month-old foal and 0.4% for the yearling. Feed protein quality is of less importance as the growth potential decreases with age and the proportion of hay in the diet increases simultane- ously.

3.4. Tables of recommended allowances and intake (Tables 11-13)

The daily allowances are set up to allow an easy calculation of the rations. These tables are different for light and heavy breeds. There are no tables for ponies as there are not enough avalaible data. The allowances are given for different body weight in each breed 450- 500-550--600 kg for light breeds; 700-800 kg for heavy breeds. In all the situations, the mare, the stallion, the gelding and the growing and fattening horse are considered in their own physiological situations: maintenance, pregnancy, lactation, mating or not, growth or fattening, rest and exercise. The allowances are given only for winter period as it is the only period studied in the breeding horses.

The recommended allowances suggested by INRA (1984) were revised by INRA (1990), mainly for the mares and the growing horses as there were more avail- ables scientific data to define requirements and new feeding strategies.

The range of amount of daily feeds suggested in the tables does not represent the maximum amount of feeds that the horses are able to consume (Bigot et al., 1987; Doreau et al., 1990) but only the amount to cover the nutritional requirements. These amounts of daily feeds are consistent with the ingestibility of the forages for all the intakes were measured in feeding trials in animals fed different diets (Table 14).

Consequently, formulating rations for horses are quite easy with these new modem INRA systems. UFC and MADC value of feeds are additive as there is no forage - concentrate interaction on organic matter digestibility of the ration (Martin-Rosset and Dulphy,


Table 14 Ingestibility I of the main forages in the growing horses and adult horses a

Feed Intake (2) kg DM/100 kg live weight

Fresh natural meadow 1.8-21. Hays: grassland-gramineous 1.7-21. Hays: legumes 2.1-2.3 Straw 1.2-1.5 Maize silage well preserved

25% DM 0.9-1.2 30% DM 1.2-1.6

Grass silage well preserved (natural meadow) 25% DM 1.2-1.5 35% DM 1.4-1.7

DM: Dry matter. i Maximum intake when the forage is offered alone ad lib. ~- The range represents the averaged variation between animals and

according to the quality of the forage offered. a From INRA, 1990.

zation of nutrients for maintenance. The validity of the system was tested extensively by INRA in the years 1985-1992.

With more understanding of the proportions of proteins digested in the small intestine for various types of feedstuffs and the ability of horses to absorb limited

amounts of microbial AA in the large intestine and use

NPN, the protein value of feedstuffs can be corrected

when portions of the protein are recovered in the large intestine. But the true digestibility coefficient of protein in the small intestine must be refined as pointed out by recent investigation (Potter et al., 1992) and the absorption of AA in the large intestine must be checked

as well, to improve the accuracy of the coefficient for correction in the next future.

Recommended energy and protein allowances are consistent for maintenance, growth and lactation. Con- versely, allowances for exercise in light horses, need to

be defined more accurately namely for intense work.

1987). These systems allow an easy formulation of rations by hand with a graphical method (INRA, 1990) which is necessary to understand, to teach and to advise on the approach to ration formulation. But a ration calculation software package "the chevalration"

developed by teachers (Tavernier and Arslanian Chev- alration: Cereopa, 16 rue Claude Bernard, 75231 Paris, France) and INRA workers both involved in the prep- aration of the new handbook entitled "Alimentat ion des chevaux"* INRA, 1990, is most accurate and eas- iest for formulating well balanced rations.

4. Conclusion

The pecularities of digestion and metabolism in the

horse do not make it possible to consider that energy value of feedstuffs is the same as for ruminant as is

stated in most systems, with the exception of the German system (Lowe and Meyer, 1982) and the American system (NRC, 1978 and 1989). The differ-

ences in utilization of digestion end products (glucose, VFA, etc.) involve large variations in the efficiency of DE and ME utilization and justify expression of the energy value of feedstuffs in NE. The new INRA energy system is based on the proportions of end-products of digestion of feeds and on the metabolic utili-

References

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Anderson, C.E., Potter, G.D., Kreider, J.L. and Courtney, C.C., 1983. Digestible energy requirements for exercising horses. J. Anim. Sci., 41 : 568-571.

Andrieu, J. and Demarquilly, C., 1987. Valeur nutritive des fourrages: tables et pi6vision. Bull. Tech. C.R.Z.V. Theix INRA. 70, 61-73.

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Documents

The French horse feed evaluation systems and recommended ... · Tables of recommended allowances have been set up by INRA for mares, growing or working horses of light or heavy breeds